Electrical switching device employing a vaporizable conductive element

ABSTRACT

An electrical switching device for causing a relatively large current to flow in response to a low voltage impulse comprising a cavity formed of two spaced electrodes surrounded by an insulating cylindrical member. At least one conductive element is located within the cavity and provided with leads extending through a removable insulating plug mounted within one of the electrodes. When a low voltage impulse is applied across the leads, the conductive element is vaporized forming an ionized gas within the cavity thereby permitting the flow of current between the electrodes.

. p i United States Patent 1191 [111 3,791,298

Amberny 'Feb. 12,1974

[ 1 ELECTRICAL SWITCH 1N6 DEVICE 3,181,464 5/1965 -,Parker et a1. 102/28 EB EMPLOYING A VAPORIZABLE 3,158,098 11/1964 Reithel 102/28 EB 3,100,447 8/1963 Betts 102/28 EB CONDUCTIVE ELEMENT 3,277,824 10/1966 Bankston 337/17 X [75] lnventor: Philippe Paul Roger Armand 2,723,324 11/ 19 55 Barnett et a1... 337/14 Amberny, Bourges, France 3,134,329 1 5/1964 Zeman 102/28 EB [73] Assignee: Etat Francais,Paris, France Prim Examiner Bemard A. Gilheany [22] Filed: Jan. 18, 1972 Assistant ExaminerA. T. Grimley Attorney, Agent, or Firm-Stevens, Davis, Miller &

21 A 1. N 21 7 1 1 pp 0 8,84 Mosher [30] Foreign Application Priority Data [57] ABSTRACT Jan. 18, 1971 France 71.01517 An electrical Switching device for causing a relatively [52] U S CI 102,281; 337/18 337/30 large current to flow in response to a low voltage im- [511' F42b 7 Holh 37/76 pulse comprising a cavity formed of two spaced elec- [58] I Fie'ld l1 4 17 21 28 30 trodes surrounded by an insulating cylindrical mem- '"'i' her. At least one conductive element is located within the cavity and provided with leads extending through 56] Reerences Cited a removable insulating plug mounted within one of the electrodes. When a low voltage impulse is applied UNITED. STATES PATENTS across the 1eads,the conductive element is vaporized 3,462,633 8/1969 MCCOY v 102/28 EB X an ionized gas within the cavity thereby per- A; g a 28 3 2 mitting the flow of current between the electrodes. e S C a 8/1965 8 Claims, 3 Drawing Figures Zeman et a1 102/28 EB X ELECTRICAL SWITCHING DEVICE EMPLOYING A VAPORIZABLE CONDUCTIVE ELEMENT BACKGROUND OF THE INVENTION This invention relates to an electrical Switching device for causing a relatively large amount of power to flow in response to a low voltage impulse. The device has many applications in the electrical and electronic fields.

Known devices of this type include the spherical spark gap wherein one sphere is moved toward the other manually or by the'use of an electromagnet. Such systems are disadvantageous in that they are bulky and difficult to synchronize.

Switches are also known which employ a gas under pressure; however, these devices tend to be unduly sensitive and the gas can become accidentally conductive due to the passage of ionized radiation. Also, control is accomplished by the application of a relatively high voltage and operation cannot be accomplished unless the voltage between the two principal electrodes is reduced to a relatively low value.

Pyrotechnique switches using the conductivity of a jet of a hollow charge are also known. These devices function but once and create a shock wave which is sometimes damaging to the system.

SUMMARY OF THE INVENTION The present invention overcomes these disadvantages in that a relatively large amount of power can be switched by a low voltage impulse. This switching occurs within a partial vacuum and over a wide range of voltages, the partial vacuum permitting the volume and mass of the switch to be considerably reduced.

The switch of the subject invention comprises a cavity defined by the surfaces of two spaced electrodes and an insulating means. Within the cavity, and electrically insulated from the electrodes, is mounted a conductive means or element arrangedto receive a voltage pulse from an external source. When a pulse is applied to the conductive element, the element vaporizes to form a higher ionized gas within the cavity. Consequently, if a voltage has been applied across the electrodes, current will flow within the cavity between the electrodes.

The conductive element can be formed of a fine metallic wire or a metallic ribbon which vaporizes when the relatively intense electric current produced by the voltage pulse flows therethrough. This results in the formation of a volume of highly ionized gas, or plasma, which permits the establishment of an electric current between the electrodes.

Thus, an object of the present invention is to provide apparatus for switching electric power wherein a conductive element is vaporized by a low voltage impulse to produce a strongly ionized gas. The device can be enclosed in a protective case which is put under partial or total vacuum and contains a gas that is readily ioniz-. able. The invention is also connected with an arrangement including a plurality of conductive elements which can be independently energized to permit a number of control functions to be obtained. These conductors can be mounted on an interchangeable support.

BRIEF DESCRIPTION OF THE DRAWING FIG. 2 is'a plan view of a second embodiment of the invention, and

FIG. 3 is aschematic diagram showing a circuit fo I energizingthe device of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1,'a cavity 11 containing air under a pressure of 10 mm of mercury is formed by two electrodes 12 and 12a spaced apart along a longitudinal axis approximately 0.5 millimeters and surrounded by an insulating cylinder 13. Electrode 12 is in the form of an annulus having at its center an insulating plug 14. Two conductors, or leads, 15 pass through plug 14 and are connected to the ends of a fine wire 16 located within cavity 11. Wire 16 may be formed of a pure metal, such as platinum, or an alloy such as iron-nickel.

When a voltage impulse is applied across leads 15 the wire 16 vaporizes thereby producing a highly ionized gas within cavity 11. Consequently, current can flow between the electrodes 12 of the device. In operation, a voltage impulse of 50 volts furnished by a 32 [.LF capacitor connected across the conductors l5 permit the switching of a voltage in the range 0.1 to 10 KV through a resistance of 5 ohms taken across the leads of a 50 nF capacitor.

FIG. 2 shows a plan view of a device similar to FIG. 1 wherein three leads 15', 15", and 15" are mounted within a plug 14. A wire 16 is connected between leads 15' and 15" and a wire 16" is connected between 15" and 15".

A circuit for energizing wires 16' and 16" is shown in FIG. 3 comprising a voltage source 17 connected in series with a resistor 18 across a capacitor. 19. Controlled rectifiers 20' and 21" are connected in series with wires 16' and 16" respectively across capacitor 19, the gates of rectifiers 20' and 20" being sequentially energized by suitable control voltages E and E which cause the rectifiers to conduct and sequentially vaporize wires 16' and 16". In a typical circuit, voltage source 17 has a magnitude of volts, resistor 18 is 100 kilohms and capacitor 9 is 0.1 P. The signals applied to the gates of rectifiers 20' and 20 should be spaced by an interval of at least 50 milliseconds when this circuit is employed.

A larger number of conductive elements may also be used and energized sequentially to provide a rapid electrical switching system. A commutator may be employed in such an arrangement wherein, after a wire had been vaporized by the application of a voltage pulse, the commutator is rotated and a new wire placed between the leads.

What is claimed isi 1. An electrical switching device comprising a. first and second electrodes spaced apart along a longitudinal axis of said device, said second electrode being in the form of an annulus having its axis coincident with said longitudinal axis;

b. an insulating hollow member affixed to said electrodes to form a cavity defined by the opposite surfaces of said electrodes and the inner surface of said hollow member;

c. an insulating plug secured to said second electrode within the annulus thereof; and

d. a plurality of electrical conductors positioned within said insulating plug and electrically connected within said cavity, said electrical conductors being vaporized when a relatively low voltage impulse is applied thereacross to form a highly ionized gas within said cavity, the ionization of said gas permitting an electric current'to flow within said cavity between said first and second electrodes.

- 2. The device defined by claim lwherein said electrical conductors comprise an element formed of a fine metallic wire.

3. The device defined in claim 1 wherein said electrical conductors comprise an element formed of a metallic ribbon.

4. The device defined by claim wherein said insulating hollow-member comprises a cylinder and said first and second electrodesare mounted at each end of ond and third leads within said cavity. 1 

1. An electrical switching device comprising a. first and second electrodes spaced apart along a longitudinal axis of said device, said second electrode being in the form of an annulus having its axis coincident with said longitudinal axis; b. an insulating hollow member affixed to said electrodes to form a cavity defined by the opposite surfaces of said electrodes and the inner surface of said hollow member; c. an insulating plug secured to said second electrode within the annulus thereof; and d. a plurality of electrical conductors positioned within said insulating plug and electrically connected within said cavity, said electrical conductors being vaporized when a relatively lOw voltage impulse is applied thereacross to form a highly ionized gas within said cavity, the ionization of said gas permitting an electric current to flow within said cavity between said first and second electrodes.
 2. The device defined by claim 1 wherein said electrical conductors comprise an element formed of a fine metallic wire.
 3. The device defined in claim 1 wherein said electrical conductors comprise an element formed of a metallic ribbon.
 4. The device defined by claim 10 wherein said insulating hollow member comprises a cylinder and said first and second electrodes are mounted at each end of said cylinder.
 5. The device defined by claim 1 wherein said cavity is maintained under a partial vacuum.
 6. The device defined by claim 1 wherein said cavity contains an easily ionizable gas.
 7. The device defined by claim 1 wherein said plurality of electrical conductors comprises first and second leads connected by a fine metallic wire within said cavity.
 8. The device defined by claim 1 wherein said plurality of electrical conductors comprise first, second and third leads, said first lead being connected to said second and third leads within said cavity. 